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Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
Parallel rays coming into a parabolic mirror are focused at a point F. The vertex is V, and the axis of symmetry passes through V and F. For off-axis reflectors (with just the part of the paraboloid between the points P 1 and P 3), the receiver is still placed at the focus of the paraboloid, but it does not cast a shadow onto the reflector.
An off-axis optical system is an optical system in which the optical axis of the aperture is not coincident with the mechanical center of the aperture. The principal applications of off-axis optical systems are to avoid obstruction of the primary aperture by secondary optical elements, instrument packages, or sensors, and to provide ready access to instrument packages or sensors at the focus.
In third-order astigmatism, the tangential rays (in the tangential plane) and sagittal rays (in the sagittal plane) form foci at different distances along the optic axis. These foci are called the tangent focus and sagittal focus, respectively. In the presence of astigmatism, an off-axis point on the object is not sharply imaged by the optical ...
Main types of parabolic antennas. An offset dish antenna or off-axis dish antenna is a type of parabolic antenna.It is so called because the antenna feed is offset to the side of the reflector, in contrast to the common "front-feed" parabolic antenna where the feed antenna is suspended in front of the dish, on its axis.
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
Several different off-axis configurations are used for radio antennas. [10] Another off-axis, unobstructed design and variant of the Cassegrain is the 'Yolo' reflector invented by Arthur Leonard. This design uses a spherical or parabolic primary and a mechanically warped spherical secondary to correct for off-axis induced astigmatism.
The first were proposed in 1935 by Maurice Paul. [1] The basic idea behind Paul's solution is that spherical mirrors, with an aperture stop at the centre of curvature, have only spherical aberration – no coma or astigmatism (but they do produce an image on a curved surface of half the radius of curvature of the spherical mirror).